As is known, a longwall mining machine traverses a coal seam or the like and has two rotating cutter heads at its opposite ends which cut and remove the coal and direct it onto a face conveyor extending along the path of travel of the mining machine. In the usual case, the mining machine is supported on tracks or guideways incorporated into the face conveyor. At opposite ends of the seam being mined are mine roadways which extend perpendicular to the face of the seam and are usually of a greater height than the seam itself. These roadways must also be cut by the rotating cutter heads carried on the mining machine.
In the past, longwall mining machines such as that shown in U.S. Pat. No. 4,085,974 have been provided with vertically-adjustable support arms for the cutter drums so as to enable the mining machine to shear a seam up to its full thickness in a single cut and to also cut the roadway at the opposite ends of the face. Vertically-adjustable support arms of this type, however, increase the overall length of the longwall mining machine and impair its maneuverability underground.
It is also possible, of course, to elevate the opposite ends of the track traversed by the longwall mining machine such that the entire machine is elevated in the roadway areas. This enables cutter drum support arms of ordinary length to be used to clear both the roof and the floor of the roadway. An arrangement of this type, for example, is shown in German Patent Specification No. 2,324,101. A machine track which rises similarly to a ramp at the ends of the face area, however, makes it considerably more difficult to load the cut material accumulating in these areas.
Drifting or heading machines having swing arms in the form of two tubular elements arranged one inside the other for telescopic movement form part of the prior art (German Auslegeschrift No. 1,221,172).